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Old 01-06-2014, 10:07 AM   #1
Default RacingBrake caliper upgrade MZ4 Coupe

A quick tip for those who will purchase this kit for the MZ4:

1. The rear two piece lines for the MZ4 Coupe comes with a choice of an angled banjo adapter and a straight banjo adapter. Use the angled one. I am going to make a suggestion to RB to just include the angled one.

2. To facilitate the rear caliper install, loosely attach the angled banjo adapter to the line with the swivel fitting, loosely attach the banjo adapter with the copper washers to the mounted caliper, then do your magic with attaching the line to the bracket, then the 2nd line to the bracket AND the chassis fitting. Tighten the swivel fitting by hand with an 11mm wrench, do not over-tighten. Then tighten the banjo fitting to 15 ft-lbs.

3. For an OEM like fit using the factory mounting bracket, which is recommended by ME because this will prevent the line from coming into contact with various moving parts in the rear, you should follow the steps above. If you choose not to use the factory mounting, you can attach the two lines together ahead of time, and zip tie the lines to the rear trailing arm. This method will make sure there's minimum fluid loss and prevent air from entering and getting trapped in places you don't want it getting trapped.

Got the full front and rear kit installed over the weekend, haven't had a chance to go bed in the brakes due to a long list of "honey dos." And I mean LONG list. Managed to squeeze in the caliper install when wife and kid are in church which in itself is a huge accomplishment, if you ask me.

Install went without a hitch. About as straight forward as you can imagine, except for the funky design of the rear brake line on the MZ4 Coupe. I think the MZ4 and the MZ3 are the only BMWs that I've ever seen with this weird 2 piece rear brake line, and on the MZ4 it's bolted to a bracket first, then a compound hard line/rubber line to the fitting on the chassis side. RacingBrake took extra care in providing an MZ4 specific rear brake line with two choices for banjo fitting, one straight and one angled. The angled fitting works much better to clear all the components in the rear and make sure nothing rubs as the suspension moves up and down. But due to the two piece line being bolted to the bracket, I had to basically work blind to thread the 2nd line on while the system is open, and on the rear driver's side it took much longer than necessary and it made a sizable mess with brake fluid everywhere.

The rear caliper was so light, that it wouldn't trigger the digital bathroom scale I was using. I ended up having to put on a heavy box first, measure it, then put the caliper assembly in. The factory caliper, pads, carrier, and lines weigh a total of 8.8 lbs. The box and the RB rear caliper, pads, carrier and lines weight 14.2 lbs, and the box itself weighed 7.4 lbs, so that makes the entire RB rear assembly 6.8 lbs. 2 full lbs lighter than the OE caliper. Pretty impressive. So if you're doing strictly the caliper upgrade along, the full kit saves a total of 8 lbs up front, 4 lbs in the rear for a total of 12 lbs of unsprung mass.

Due to the extended time the line was cracked open when I was having trouble threading on the second line, I suspect some air may have gotten into the ABS unit. I'm going to see if my friendly mechanic has time this weekend to cycle the pump just for sh*ts and giggles, and re-bleed that corner again. Then I'll go fully bed in the pads. Otherwise it wouldn't be entirely fair to give an assessment from moving the car around in the driveway. But based on the few quick pumps of the pedal while moving the car, I have to say, I'm impressed. The pedal is rock freakin' solid with a very direct feel, without any of that 1/4" of dead travel the OEM system has always had since new. We'll see how it behaves with the slotted RB rotors, with the flex/float design of the OEM caliper there's always a vibration in the pedal upon heavy brake application on track. I suspect the fixed caliper design will go a long way to alleviate.

I have to say, I'm very impressed with the amount of hardware they provided for the rear. Typically for these sort of kits, most won't even bother with the compound line, and just provide you with a long braided brake line and expect the experts installing the kit to zip tie it where and when appropriate. My experience with this car though, since the rear line is tied to the rear trailing arm, when the trailing arm moves, the line flexes and moves and MAY come in contact with the rear tire, especially if you're running super wide tires. When I used to run a stainless steel braided line on the MZ4 Coupe, I noticed one of the rear lines were slowly being worn away...In long, fast, and heavy sweepers the tires deflect far enough and the brake line moved enough to come in contact with the tire. :bulge: I suspect that is why BMW provided a hard, rigid line as part of the rear brake hydraulics, so there's zero chance of anything flexing out far enough to come in contact with a wider than factory tire (275 wide).

They (RB) certainly went above and beyond to make sure it fit our cars properly. This kit probably could have been released 6-8 months ago but they kept making minor changes to make sure they FIT. I have to applaud RB for that.:thumsup:
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